Diodes are uniquely efficient sources of diffraction-limited light. However, diode lasers are limited today to approximately 1 watt (W) in single-mode emitted power, preventing their direct application to directed energy and other important applications. Spatially single mode diode lasers emitting 10 W or more are needed for diverse applications.
Certain practical directed energy systems are predicated on the availability of efficient single-mode continuous wave (cw) lasers at 10 kilowatts (kW) and above. Diode lasers are capable of 50% to 75% power conversion efficiency, but, to date, power scaling of diode lasers beyond 1 W remains an elusive goal, whereas efficient combining of 104 or more independent array elements to achieve a single-mode cw source may not be practical.
As today's applications at or above 10 kW become increasingly important, the opportunity to return to 50% or higher efficiency beam-combined systems powered by up-to-75% efficient single-mode diode lasers becomes increasingly relevant to meeting real system requirements. Thus, any opportunity to increase single-mode power significantly beyond 1 W is crucially important.